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Nodular Pneumocystis carinii pneumonia in SIV-infected macaques
Abstract:
Pneumocystis carinii (PC) pneumonia is a frequent manifestation of the acquired immunodeficiency syndrome (AIDS) in humans and macaques. An unusual nodular type of PC pneumonia was observed in two simian immunodeficiency virus (SIV)-inoculated rhesus macaques (Macaca mulatta). These animals developed clinical signs of simian AIDS, including anorexia, weight loss, dyspnea, and collapse. Grossly, both animals had multifocal tan-white nodules 1-10 mm in diameter scattered throughout the lungs. One animal had similar nodules involving the diaphragm and thoracic wall. The lungs were characterized by severe PC pneumonia with numerous large nodules consisting of foamy material that compressed adjacent tissue. The nodules had central areas of necrosis and lysis of alveolar septa. Varying degrees of necrotizing vasculitis were observed in areas of nodular PC pneumonia. The presence of PC in intra-alveolar spaces and nodular lesions was confirmed by immunohistochemistry. No evidence of other agents, including viral inclusions, bacteria, fungi, and lung mites, was detected. The animal with the most severe nodular PC pneumonia had vascular involvement with extrapulmonary spread to the diaphragm, thoracic wall, and regional lymph nodes. This unusual type of nodular PC pneumonia has been rarely seen in human AIDS patients.
Insights
An unusual nodular form of Pneumocystis pneumonia was found in rhesus macaques with simian AIDS. This rare presentation involved lung nodules and extrapulmonary spread, offering insights into AIDS-related opportunistic infections.
Area of Science:
- Veterinary Pathology
- Immunology
- Infectious Diseases
Background:
- Pneumocystis pneumonia (PCP) is a common opportunistic infection in immunocompromised individuals, including those with acquired immunodeficiency syndrome (AIDS).
- Simian immunodeficiency virus (SIV) infection in macaques serves as a model for human immunodeficiency virus (HIV) infection and AIDS.
Observation:
- Two rhesus macaques inoculated with SIV developed clinical signs consistent with simian AIDS.
- Multifocal tan-white nodules, 1-10 mm in diameter, were observed throughout the lungs of both animals.
- One macaque also exhibited similar nodules on the diaphragm and thoracic wall.
Findings:
- Histopathological examination revealed severe Pneumocystis carinii pneumonia characterized by large, foamy nodules compressing lung tissue.
- Nodules showed central necrosis and lysis of alveolar septa, with necrotizing vasculitis noted.
- Immunohistochemistry confirmed the presence of Pneumocystis carinii within intra-alveolar spaces and nodular lesions, excluding other pathogens.
Implications:
- This case report describes a rare nodular form of Pneumocystis pneumonia in SIV-infected macaques, mimicking presentations seen in human AIDS patients.
- The extrapulmonary spread observed in one animal highlights the potential severity and invasive nature of this atypical presentation.
- Understanding this unusual manifestation can improve diagnostics and disease management in both animal models and human AIDS cases.